Thanks for the fast response. The only 2 plugins installed are
Fast Secure Contact Form, and LBAK User Tracking.

I thought I had tested with one and then the other disabled, but apparently I didn't disable LBAK User Tracking. With that disable, I am able to use the "Add" function. Not sure why there is a conflict there.

Once I enabled it again, the "Add" feature stopped working again. Disabling LBAK User Tracking brings full functionality back, almost.

While everything now shows up, creating a new level or subscription, just returns me to the list with no level or subscription created, even though it appeared to add it.

That sounds like the LBAK User Track plugin is probably loading some js in areas it shouldn't. Your best bet is to contact that developer and let them know of the issue.

You can enable the console and script tag in firebug and check out the error for yourself and report it to their developers.

In the least I'd recommend disabling it for the entire time you're working with the membership settings area.

On the "Edit - new level" page after adding the rules you should be able to click the 'add' button at the bottom and see it added to your list of levels. It also should be labeled 'inactive' by default.

You may want to create a new thread on this matter as there may be a lot to go through on it, but for starters you'll definitely want to ensure you're running either the latest or a somewhat recent version of WordPress.

You may also want to deactivate other plugins to ensure there's not a plugin conflict of some sort.

Thanks for the response, sorry for the delay in replying. I think my problem was a simple misunderstanding about not activating the plugin. When I activated it in the plugins section I eventually found the tab on my dashboard (I wasn't expecting it to be right at the top either) and noticed there is an activate link on the membership tab too. Overall, my problem is resolved, no thanks to a bit of buffoonery! Could this be made clearer in your installation instructions?